Performance Analysis of Double-Channel 802.11n Contending with Single-Channel 802.11

Due to their ease of deployment, 802.11 networks are widely used. To cope with increasing throughput requirements, and to take advantage of improvements in hardware performance, 802.11n has been introduced. One of the extra features is the 20/40 functionality, which allows 802.1 In devices to operate using one or two 802.11 channels. In this paper, we study the contention rules for such 20/40 operation on top of the 802.11 Distributed Coordination Function (DCF). We then study the performance of double-channel users in presence of single-channel 802.11 users. Similar to the 802.11 model introduced by Bianchi, we introduce a Markov model for both the legacy 802.11 and double-channel 802.11n users. To couple the Markov models of both types of users, we have to understand how to relate virtual time slots of both types. Next, we introduce collision rules that capture traditional in-channel 802.11 collisions as well as collisions between the different types of users. This allows us to complete the analytical throughput model for 802.11 and double-channel 802.11n users when they coexist. The conclusions are important for understanding 802.11 networks in particular, but also for contention of heterogeneous devices in general.